[Security Solution] Modify copy of the install rules title and message (

#202226)

**Resolves: #200521**

## Summary

I am changing the copy of the install rules title and message.

# BEFORE

![image](https://github.com/user-attachments/assets/3d22a93a-3a37-4e1a-a187-eda609daf625)

<img width="873" alt="image"
src="https://github.com/user-attachments/assets/5f4b82f1-094e-432f-9d25-c31042b7585b">

# AFTER
<img width="611" alt="image"
src="https://github.com/user-attachments/assets/bf211743-2edc-4573-8d10-1c156000d875">

<img width="791" alt="image"
src="https://github.com/user-attachments/assets/612b90b1-290d-40e5-96eb-c88182f78673">


### Checklist

Check the PR satisfies following conditions. 

Reviewers should verify this PR satisfies this list as well.

- [X] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/packages/kbn-i18n/README.md)

---------

Co-authored-by: Nastasha Solomon <[email protected]>

x-pack/plugins/security_solution/public/detection_engine/rule_management_ui/pages/add_rules/translations.tsx

@@ -10,6 +10,6 @@ import { i18n } from '@kbn/i18n';
 export const PAGE_TITLE = i18n.translate(
   'xpack.securitySolution.detectionEngine.rules.addRules.pageTitle',
   {
-    defaultMessage: 'Add Elastic Rules',
+    defaultMessage: 'Add Elastic rules',
   }
 );

x-pack/plugins/security_solution/public/detections/components/rules/pre_packaged_rules/translations.ts

@@ -10,15 +10,15 @@ import { i18n } from '@kbn/i18n';
 export const PRE_BUILT_TITLE = i18n.translate(
   'xpack.securitySolution.detectionEngine.rules.prePackagedRules.emptyPromptTitle',
   {
-    defaultMessage: 'Load Elastic prebuilt detection rules',
+    defaultMessage: 'Install and enable Elastic prebuilt detection rules',
   }
 );
 
 export const PRE_BUILT_MSG = i18n.translate(
   'xpack.securitySolution.detectionEngine.rules.prePackagedRules.emptyPromptMessage',
   {
     defaultMessage:
-      'Elastic Security comes with prebuilt detection rules that run in the background and create alerts when their conditions are met. By default, all prebuilt rules except the Endpoint Security rule are disabled. You can select additional rules you want to enable.',
+      'Elastic Security comes with prebuilt detection rules that run in the background and create alerts when their conditions are met. To start using them, choose rules to install and enable.',
   }
 );